The invention relates to an iron alloy composition as a wear-resistant coating on a brake disc, a wear-resistant coated brake disc and the production thereof.
A wear-resistant, coated, substantially metallic vehicle component having a friction surface, for example a brake disc, is known from WO 03/104513 A1. The friction surface is formed by a wear-resistant top layer which substantially consists of molybdenum, wherein a typical composition has more than 99% molybdenum. A bonding layer is applied to the base substrate of the component in order to connect the top layer to the base substrate. However, a disadvantage of processing molybdenum is its high melting temperature and the high costs for molybdenum.
Therefore, for the vehicle component having the friction surface from WO 2007/043961 A1, the wear-resistant top layer is formed of an alloy which contains between 50 and 99% molybdenum, wherein the group consists of at least one of the following elements: Aluminum, boron, carbon, chromium, cobalt, lanthanum, manganese, nickel, niobium, oxygen, silicon, tantalum, tungsten, yttrium. This alloy has a liquidus temperature which is considerably lower than that of molybdenum, such that the alloy is completely or almost completely liquefied during thermal spraying, whereby the formation of a non-porous top layer is promoted. The thickness thereof is approximately 25 to 600 μm, preferably 300 μm. A connecting layer between the molybdenum top layer and the substrate substantially comprises a main portion of nickel and a low portion of aluminum. The thickness thereof can be between 0 and 100 μm, preferably approximately 50 μm.
DE 10 2008 035 849 A1 describes a method for coating brake surfaces of steel brake discs, in which a wear-resistant coating is applied to the roughened brake surfaces by thermal spraying. A spray material used for high-speed flame spraying is a ceramic-metal composite material made from tungsten carbide and a metal component, which either consists of cobalt, nickel or a cobalt or nickel alloy. In the arc spraying method, a coating made from Fe 18 Cr 8 Ni 2 Mn, Fe 13 Cr 0.5 Si or from alloyed carbon steel having a carbon content of approximately 0.35% as well as further alloy components in the form of Si, Ni, Mn, P (traces) and sulphur (traces) can be applied to the brake surfaces of the steel brake disc.
EP 1 336 054 B1 describes a brake disc and a method for the production thereof. Brake discs made from a cast iron material, for example grey cast iron having a carbon content of 3.7-4.0%, have an oxidation-resistant and wear-resistant, metallic, non-ceramic injection moulded coating made from a harder metal on at least one of the axial friction surfaces, for example a non-alloyed or alloyed steel which has carbide and oxide. The injection moulded coating can be produced by flame, arc or plasma spraying. The steel alloy used can contain Cr, the content of which in the coating can be between 10 and 20%. One composition of the coating steel has 16% Cr; 0.44% Ni; 0.43% Mn; 1.01% Mo and 0.36% C.
Based on this prior art, the object of the present invention is to provide an improved wear-resistant coating for the brake surfaces of a brake disc.
This object is solved by a wear-resistant coating on a brake disc of the present invention.
The further object of the invention, to create a brake disc whose friction surfaces link a high level of hardness with increased abrasion resistance, such that the formation of fine particles when braking is reduced, is solved by a brake disc of the present invention.
Developments of the alloy composition and the method are embodied in the respective sub-claims.